1. Field of the Invention
The present invention relates to height adjustable tables. More particularly, the present invention relates to an improved height adjustable table that provides a plurality of legs that are simultaneously adjustable. A specially configured gear and drive shaft configuration telescopes all of the legs simultaneously to either raise or lower a table top supported by the legs responsive to rotation of a single crank.
2. General Background of the Invention
Adjustable tables have been in use for many years. There are several adjustable height tables that are commercially available. Several of these adjustable height tables were patented as drafting tables. Several of these patented commercially available tables were sold under the trademark Hamilton. Patents relating to Hamilton® drafting tables that have been sold for many years are U.S. Pat. Nos. 3,140,559 and 3,273,517).
One of the primary uses for adjustable height tables is the support of a heavy object such as a computer and/or monitor at a comfortable elevation for the user. Because computers and monitors are relatively heavy, a problem exists when the table is at a maximum elevational position such as when the user chooses to stand. In such a situation, adjustable height tables can become top heavy and suffer from lateral instability. The weighted table top of the table tends to deflect when it is elevated to a high position and when it is loaded with a heavy object such as a monitor, computer or the like. In order to stabilize a table top, often three or more legs are placed in triangular position. When a table top is extremely large, three legs are preferably employed rather than two legs having laterally extending feet. For a table with three legs, height adjustment requires that all three legs either elevate or lower simultaneously. Many patents have issued that are directed to elevating or height adjustable tables. Early patents that show adjustable height tables are shown for example in U.S. Pat. Nos. 5,448,36; 1,243,750; 2,532,342; and 2,642,996;
The May Patent discloses an adjustable support for a drafting table. In the May U.S. Pat. No. 2,982,050, an adjustable drafting board support that includes a pair of links that swing to elevate and lower the board and an improved arrangement for counterbalancing the board to apply a substantially uniform lift to the board in all operative positions.
The Grow U.S. Pat. No. 3,140,559 discloses a drafting table that uses a rack and pinion arrangement in combination with a locking or braking mechanism which is adapted to lock the vertically adjustable table in any selected position when the operating linkage has been released and which lock will become even more securely locked upon the application of downward pressure on the table top occurring in normal use.
The Kooi U.S. Pat. No. 3,364,881 discloses a drafting table with a single pedal control of both vertical movement and tilting. U.S. Pat. No. 3,638,584 discloses a drafting table that includes a pedestal, support columns associated with the pedestal for vertical movement and a drafting board on an upper portion thereof. An elevating table is disclosed in the Feiertag U.S. Pat. No. 3,820,176.
A telescoping support arm of quadrangular cross-section is disclosed in the Bertalot U.S. Pat. No. 3,887,115. The apparatus provides roller bearings in corner spaces between each tube surrounding each other, the rollers in one corner rolling over separate braces supported on resilient means urging the rollers and the inner tube toward the other corner so as to exclude backlash.
The Horner U.S. Pat. No. 3,908,560 discloses a counter balancing system for a drafting table.
A vertically adjustable drafting table is disclosed in the Evans U.S. Pat. No. 4,130,069.
The Raymond U.S. Pat. No. 4,469,029 discloses a workstation comprised of support legs with a stable support base and the uprights on which pivoting elbows are adapted to form adjacent arms which are positioned and locked in place in an adjustable angular manner at one of these end of the arms, the other end bearing supports are work tops positioned and locked in place in a manner which can be angularly adjusted at will, so that these supports or work tops allow effects and uses which are multiple and can be combined together.
U.S. Pat. No. 4,591,214 issued to Reuter discloses a cabinet closure assembly that includes a panel which is pivotable between opening-blocking and opening-unblocking positions. The Kurrasch U.S. Pat. No. 4,619,208 discloses a work surface height adjustment mechanism.
An adjustable computer work table is disclosed in U.S. Pat. No. 4,637,322. Vertically actuating scissor arms are provided for moving the support shaft upward and downward whereby providing a vertical adjustment.
The Ball U.S. Pat. No. 4,751,884 discloses a height adjustable work top. The work top is adjustable and may tilt about a horizontal axis near the front edge. The work top may be mounted in an open office beam system or an office screen or partition in cantilever fashion or it may be a free standing unit.
A table lift mechanism is disclosed in the Watt U.S. Pat. No. 4,981,085. The '085 patent discloses furniture having a top or the like supported for vertical movement by telescoping legs supports with a counter balance for exerting a relatively uniform counter balance force from the top throughout its range of vertical movement. A latch mechanism is provided for latching the top in the selected vertical positions, and an adjustable roller guide mechanism as provided for coupling the telescoping elements of the legs supports.
An apparatus for adjusting a computer work station to individual needs is disclosed in the Seiler U.S. Pat. No. 5,041,770.
An adjustable height table is disclosed in the Rizzi U.S. Pat. No. 5,289,782. The '782 patent discloses a table having a top that can be vertically adjusted to various heights by a pair of telescoping legs and a counter balance weight mechanism which includes a weight box and weights that can be easily added or removed by the user depending on the weight carried by the table top. A locking mechanism including a spring urged threaded half nut and a stationary threaded rod enables the table top to be locked in place once a desired height is achieved.
An adjustable dual work surface support is disclosed in the Sherman, et al, U.S. Pat. No. 5,332,025. The Borgman, et al, U.S. Pat. No. 5,323,695 discloses a method of using a work station having separate and back tops having separate power drive arrangements while permitting independent height adjustment. A controller, which is programed by an operator, permits storage of a number of predetermined height locations each defining distinct heights for the tops. The operator effects programed movement of the tops to predetermined height locations for predetermined times in a predetermined sequence, with the rear top moving initially and a front top moving thereafter.
The Smies U.S. Pat. No. 5,339,750 discloses an adjustable work table. The '750 patent table comprises a base and at least one movable extensible vertical column attached to the base having a table top carried on the vertical column. A pivot is provided for moving the table top into any of a range of pivoted positions, preferably on both sides of the horizontal position of the table top. A motor is provided for holding the table top in any of the range of pivoted positions.
A non-binding cantilevered table lifting device disclosed in the Childers U.S. Pat. No. 5,370,063.
The Winchell U.S. Pat. No. 5,408,940 discloses an adjustable height work surface with rack and pinion arrangements.